Outlook 2019/365: Fix “Your mailbox is over its size limit” Message

If your Outlook 2019/365 mailbox is getting full you will be sent an email message to tell you that your mailbox is approaching the quota. If you do not reduce the size of your mailbox, you will be unable to send email, and you’ll receive an email that says “Your mailbox is over its size limit”.

The email quota is usually set by the Microsoft Exchange administrator within your organization. In some cases, administrators may grant you more space if you contact them. You can also use the Personal Folders feature in Outlook to store Outlook items locally on your hard drive. Items in the Personal Folder do not count toward your quota.

Of course, it’s best to keep things tidy and clean out some of the things you’ll never need. To clean out your mailbox, follow these steps.

Option 1 – Cleanup Tool

Note: These steps are for the Windows version of Outlook. This feature is not available in the macOS version.

1. Go to “File” > “Cleanup Tools” > “Mailbox cleanup“.
2. From the “Mailbox Cleanup” screen, you  can choose to “Find items older than” a certain number of days, or “Find items larger than” a certain size. Personally, I try to find items larger than 250 kilobytes, then select “Find…“.
3. The wizard searches for messages that meet your search criteria. From the “Advanced Find” screen, you can delete any unwanted items.

Once you have deleted any unwanted items, be sure to empty the “Deleted Items” folder by right-clicking it and selecting “Empty Folder“.

Option 2 – Manual Removal

1. While viewing your mail in Outlook, right-click the email address in the left pane and choose “Data File Properties“.
   
2. Select the “Folder Size…” button.
   
3. Have a look at which folders have the largest size. Use this information to target folders from which to manually clear out email messages.